1. Field of the Invention
The present invention relates generally to an enclosed type rotary compressor employable for a refrigerating unit for a refrigerator or the like, an air conditioner or the like. More particularly, the present invention relates to an enclosed type rotary compressor for cooling a lubricant oil and a compressing element, each of which is heated up to an elevated temperature during running.
2. Description of the Prior Art
FIG. 3 is a vertical sectional view of a conventional enclosed type rotary compressor as disclosed in an Examined Japanese Patent Publication (Kokai) Sho-63-39798, and FIG. 4 is a vertical cross-sectional view of the enclosed type rotary compressor taken along line A--A in FIG. 3.
In FIG. 3 and FIG. 4, reference numeral 1 designates an enclosed vessel. The enclosed vessel 1 is composed of three enclosed vessel segments, i.e., an enclosed vessel segment 1a, an enclosed vessel segment 1b and an enclosed vessel segment 1c, and a lubricant 4 is hermetically stored in the enclosed vessel 1. An electrically (hereinafter "electrically driving element") driving element 2 consists of a stator 2a and a rotor 2a, and a compressing element 3 includes as essential components a cylinder 3a, an end bearing 2b, a main shaft bearing 3c, a rolling piston 3d and a crankshaft 3e by way of which power generated by the electrically driving element 2 is transmitted to the compressing element 3. The electrically driving element 2 and the compressing element 3 are enclosed in the vessel 1. Reference numeral 5 designates an oil supplying pipe. A spirally extending oil supplying spring 5a received in the oil supplying pipe 5 is rotated by the crankshaft 3e, causing a lubricant 4 to be supplied to the compressing element 3. Reference numeral 6 designates a discharge cover for attenuating pulsating pressure wave of refrigerant gas discharged through a discharge port 3f formed through the end bearing 3b, and reference numeral 6a designates a refrigerant discharge port formed through the discharge cover 6. Reference numeral 6b designates a plurality of fixing screws each serving to fixedly securing the discharge cover 6 to the end bearing 3b. Reference numeral 7 designates a discharge pipe for supplying the refrigerant to an oil cooler condenser 8, and reference numeral 9 designates a loop-shaped oil cooler pipe of which lower part is immersed in the lubricant 4. Reference numeral 10 designates an ordinary condenser disposed in a refrigerant circuit, reference numeral 11 designates a pressure-reducing (regulator) unit, reference numeral 12 designates an evaporator, and reference numeral 13 designates a suction pipe. In addition, reference numeral 14 designates a terminal portion by way of which electricity is supplied to the electrically driving element 2. Next, a mode of operation of the conventional enclosed type rotary compressor as constructed in the aforementioned manner will be described below.
As the refrigerant gas is compressed by the compressing element 3, it is discharged into the enclosed vessel 1 through the refrigerant discharge port 6a of the discharge cover 6, and thereafter, it is supplied via the discharging pipe 7 to the oil cooler condenser 8 in which the heat of the refrigerant gas is radiated. Subsequently, the cooled refrigerant gas is introduced into the oil cooler pipe 9 of which immersed part performs heat exchanging between the refrigerant and the lubricant 4 in the vessel 1 so as to cool the lubricant 4. The refrigerant is heated again as it passes through the oil cooler pipe 9, and the heated refrigerant is delivered to the condenser 10 in which the heat of the refrigerant is radiated, causing it to be liquidized. The liquidized refrigerant is delivered via the pressure-reducing unit 11 to the evaporator 12 in which it is vaporized and then sucked in the compressing element 3 again, whereby a single refrigerating cycle is completed.
FIG. 5 is a schematic sectional view of an oil cooling mechanism employable for a conventional multistage type oil cooling screw compressor as disclosed in Unexamined Japanese Utility Model Publication (Kokai) UM-Sho-63-82081.
In FIG. 5, reference numeral 25 designates oil separators, reference numeral 26 designates oil coolers, and reference numeral 27 designates oil return lines. In addition, reference numeral 28 designates a casing. Three rotors 29 are accommodated in the casing 28, and three nozzles 30 are disposed in the casing 28 so as to allow oil to be returned to compressing chambers of the rotors 29 during a step of compressing.
With the oil cooling mechanism as constructed in the above-described manner, as the oil flows through the oil coolers 26 and the oil return lines 27, it is cooled during the compressing step in the presence of a differential pressure P.sub.1 -P.sub.2 wherein discharge pressure in each oil separator 25 is represented by P.sub.1 and pressure in a compressing chamber of each rotor 29 during the compressing step is represented by P.sub.2. After the oil is cooled, it is returned to the compressing chamber of each rotor 29 so as to compress the oil.
FIG. 6 is a schematic sectional view of an oil cooling mechanism employable for a conventional air cooling type oil supplying compressor as disclosed in Unexamined Japanese Patent Publication Hei-1-300073.
In the drawing, reference numeral 25 designates an oil separator, reference numeral 26 designates an oil cooler, reference numeral 31 designates an oil pipe, reference numeral 32 designates a cooling fan, and reference numeral 33 designates a main body of the compressor.
With the oil cooling mechanism constructed in the above-described manner, oil contained in the high pressure air discharged from the compressor 33 is separated from air in the oil separator 25, and as the oil is increasingly accumulated on the bottom of the oil separator 25, it is discharged to the oil cooler 26 via the oil pipe 31 in the presence of a differential pressure P.sub.3 -P.sub.4 wherein pressure in the oil separator 25 is represented by P.sub.3 and suction pressure of the compressor 33 is represented by P.sub.4. Subsequently, the oil is cooled by rotating the cooling fan 32, and then, it returns to the suction side of the compressor 33.
As is apparent from the above description, it is an essential condition for each of the conventional enclosed type rotary compressors as mentioned above that the rotary compressor is designed with small dimensions in order to minimize the volume of the compressor. For this reason, it is practically difficult to maintain a large space for storing the oil cooler pipe 9 enough to effectively cool the lubricant 4. For example, in case that a single compressing element 3 including a compressing chamber having a large displacement volume or two compressing elements 3 disposed at the opposite ends of the electrically driving element 2, which generate a large heat quantity, are employed for a compressor, necessary cooling properties can not be obtained with the compressor with the result that the temperature of a lubricant is elevated, and moreover, the temperature of each compressing element 3 is also elevated. Consequently, there arise serious malfunctions that the refrigerating capability of the rotary compressor is reduced due to the preheating the refrigerating gas, and the bearing is seriously damaged or injured due to reduction of the viscosity of the oil, resulting in the rotary compressor failing to operate normally.
The oil cooling unit employed for the conventional multistage oil cooling type screw compressor or the conventional air cooling type oil supplying compressor includes means for directly cooling an oil in the oil coolers 26, and after completion of the oil cooling, the cooled oil is returned to the compressing chamber of the compressor. With such construction, when the oil fails to be accumulated in any one of the oil separators because of some operating conditions or environmental conditions, the high pressure refrigerating gas to be compressed flows through the oil line to reach the compressing chamber of the rotary compressor. This leads to the result that an amount of compressing operation to be performed is substantially increased, causing a large amount of energy to be undesirable consumed.